Simplify the following expression: $y = \dfrac{9n}{10} + \dfrac{8n}{7}$
Answer: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $10$ and $7$ $\lcm(10, 7) = 70$ $ y = \dfrac{7}{7} \cdot \dfrac{9n}{10} + \dfrac{10}{10} \cdot \dfrac{8n}{7} $ $y = \dfrac{63n}{70} + \dfrac{80n}{70}$ $y = \dfrac{63n +80n}{70}$ $y = \dfrac{143n}{70}$